If you didn't keep track of the number of ranked rounds when you moved up to Legend, you'll just have to keep firing until that round with three in the water and two out of bounds doesn't increase your average.
I turned Legend after round 621 on Dec. 19. I'm not even going to worry about it until round 1121 and change (for those Par 5 rounds that don't count). At the rate I'm going, that will happen in June or July.
I'm a tad over half way, and at this point a really bad or a really good round doesn't really change the average that much.